Automotive vehicles have used gravity feed for fuel in the early stages of the industry and the next phase beyond this was a diaphragm pump in which the diaphragm was mechanically pulsed by a lever actuated by a cam actuated by the engine itself. Also, electric pumps have been used with the pumping action provided by a solenoid armature reciprocating in a solenoid winding in response to electrical contacts in a circuit responsive to the motion of the armature.
In every case there is a problem of matching the fuel supply to the demand of the engine under all conditions of operation, whether it be idling, full open throttle at high speed, or open throttle under load such as climbing a hill or moving through sand or snow where the load causes a reduced speed even with open throttle.
It is also important to have a fuel pump which will have a reliable output under all conditions of ambient temperature in winter and summer.
It is an object of the present invention to provide a constant speed rotary electric pump which can yet respond to fuel demand by the operation of a unique relief or by-pass valve at the rotary pump inlet. A further object is a rotary pump design which has a steady, even output flow with minimal surging in the output so the engine fuel mixing device can perform its function unaffected by a surging fuel supply.
Another object is a pump design which is compact and of a size to be easily mounted in a safe area in an automotive vehicle. It can be mounted in or out of the fuel tank.
Other objects include providing a pump relief system which can provide a substantially constant pump outlet pressure even though the outlet flow may vary from the maximum desired flow to a minimum flow.
The pump incorporates a simple pressure regulator valve in conjunction with pulse absorption device to provide a smooth flow of fuel. The pressure relief valve is designed for an initial lift-off in response to pump pressure and automatically expose additional area to the pressure to steady the by-pass and avoid an erratic or jerky "hunting" for the desired pressure. Attention is directed to U.S. patents to Catterson, U.S. Pat. No. 3,415,195, dated Dec. 10, 1968, and O'Connor, U.S. Pat. No. 3,470,824, dated Oct. 10, 1969, where a magnetic relief valve plate is utilized in conjunction with a rotary fuel pump.
A further object is the provision of a retainer shell which holds the respective parts together under resilient compression in a sealed relationship.
A further object of the invention is the provision of a pump outlet plate having a spherical bearing seat for a motor shaft which permits self-alignment, and a relief valve plate formed on the pump inlet plate cooperating with a pressure plate to permit by-pass of outlet pressure to the inlet side of the pump under controlled conditions.
Other objects and features of the invention will be found in the following description and claims in which the principles of the invention are set forth, together with a detailed description and parts which make up the operating assembly, all in connection with the best modes presently contemplated for the practice of the invention.